Pour enough vegetable oil in the skillet or pot until it reaches 2 to 3 inches deep. Heat the oil to 350º F, checking it with a candy thermometer or a instant digital thermometer.
In a medium bowl, mix Bisquick, milk, eggs, and vanilla extract together until the mixture is smooth. The mixture should have the consistency of cake batter and free of lumps.
Fry the funnel cakes
Pour funnel cake mixture into a pastry bag or Ziplock bag and seal the top. If using a Ziplock bag, cut the tip from one edge of the bag (about 1/2"). Starting in the middle of the pan or pot, squeeze the batter in a circular swirling motion, creating ribbons of batter to create a 5-inch wide funnel cake.
Let the funnel cake fry until the bottom of it is golden in color, about 1 minute, then use tongs or a spatula to carefully turn it over. Cook the other side until it is equally golden, about 45 seconds to 60 seconds.
Use this same process to make the rest of the funnel cakes.
Carefully remove cooked the funnel cakes with tongs and let rest on a paper-towel lined plate to wick away excess oil.
To serve
Sprinkle with powdered sugar, whipped cream, or cinnamon sugar, or your favorite toppings, and serve warm.
Notes
Make your own Bisquick with my DIY baking mix recipe (linked). *Nutritional facts are calculated without frying oil